The present invention relates to the display of alphanumeric or graphic information by an image reproducing device such as a kinescope, and, in particular, to a system and method for controlling the video level of an image reproducing device depending on the region and the content of the information being displayed.
Electronic devices such as televisions and personal computers (PC) typically require a video monitor and associated video display controller/processor for displaying images so that information can by conveyed to the users. The present inventor has recognized that, however, the differences in the nature and the content of the material to be shown place disparate requirements on the display. For example, two types of material with different requirements are:
1. Text and line-oriented graphics: These require very sharp video edges, such as black-to-white and white-to-black transitions, and therefore, need a very well-focused, crisp display. These types of materials also tend to have a large percentage of their content displayed at full brightness. Black text on white background is typical, simulating print media on white paper. Since cathode-ray-tubes tend to have larger electron spots at high currents, causing xe2x80x9cbloomingxe2x80x9d and poorer focus, these types of material should be displayed at lower beam currents. This is typical of the way that computer desktop monitors are operated.
2. Real-world photographic-style or television broadcast images; These tend to naturally have softer edges, and so do not have the same requirement for the very sharp focus that text and line graphics do. It is another characteristic of this material that it typically has a lower duty cycle of high brightness material (i.e., most of the video is not at full brightness), but a few bright peaks are required to give the material a realistic xe2x80x9cpunchxe2x80x9d and vividness. This is typical of the way that commercial television receivers are operated. To obtain that realism, the highest level of brightness for this type of material should be displayed at a higher brightness level than the text and graphics as described above.
In EP-A-0729273, a television set is disclosed having the capability to adjust a display parameter for either the main or a PIP image. Likewise in EP-A-0569018, a television set is disclosed which independently adjusts a display parameter of a main display and a sub-display. Both of these disclosures, however, adjust the display parameter based on the instantaneous determination of the real time signal being processed. In addition, neither of these references show any recognition that the signal being processed may be from a source other than a television.
The present inventor has recognized that a problem arises when a display must exhibit both types of material, each of which has its own requirements. This type of setup is found for example, in a device which combines the functions of a personal computer (PC) with a television. For example, a personal computer can be outfitted with a television tuner card, so that a user may watch a television program in one window of provided by the computer""s graphical operating system (e.g., Microsoft Windows 95(copyright)), while working on a spread sheet application displayed in another window. Another example is a television receiver which is also being used as a PC monitor or has built-in PC capabilities for surfing the internet or performing other computing functions. Video drive level adjustments need to be made to optimize each of the material being displayed.
Another situation where a display must exhibit both types of material is, for example, when a television has an electronic program guide or some other text/graphical On Screen Display (OSD) information that needs to be conveyed to the users, along with real-world, television broadcast information. In addition, such a television may include internet access so that computer graphics and text can be downloaded from the internet for viewing on the television display. The computer graphics and text may be displayed, for example, in a subpicture of a television with a Picture-in-Picture (PIP) or Picture-out-of-Picture (POP) capability, while the main picture is showing the television broadcast channel. These different viewing materials may each require a different drive level to provide the proper picture on the same screen.
The inventor has recognized that drive level adjustment between two or more types of material may be made manually, if only one is shown on the display at a time. This might be done with the monitor""s contrast control, for example. However, with systems such as those that combine the functionality of a PC and TV, it is common that more than one type of material will appear on the screen simultaneously. For this reason, it is desirable for the system to be able to adjust the video drives for each type of the display material in each region of the display screen automatically and independently, depending on the content of the material being displayed.
Accordingly, a video processing system and method is provided for presenting an image having more than one region on a display. The system has a control processor which can determine, for each region, the type (e.g., graphics, text, computer programs, broadcast TV video, etc.) of the image material being displayed in the region. The system also has a video driver coupled to the display for providing image signals having contrast and brightness characteristics. The control processor generates a control signal for causing the video driver to adjust the contrast and brightness characteristics of the image signals according to the type of material being displayed in the region.
Another aspect of the present invention provides for manual adjustment of the image characteristics for each of the regions independently, therefore, allowing a user to adjust the drive level for each region to suit his or her own taste.